The long-term goal of these studies is to understand the role of types IX and XII collagens in establishing and maintaining the structure of extracellular matrices, the modulated expression of their genes during normal embryonic development and alterations in diseases such as osteoarthritis. These multi-domain collagens are among the quantitatively minor extracellular matrix components of tissues such as cartilage, tendons, skin and cornea, but their unique structure and localization within the matrix suggest a specific role in the three-dimensional network structure of the matrix. To reach this goal, we will use a combination of DNA cloning/sequencing and protein chemistry to complete the structural characterization of types IX and XII collagens. Specific polyclonal and monoclonal antibodies will be raised against purified protein as well as synthetic oligopeptides ad such antibodies will be used to localize the collagens in tissues using light and electron microscopical immunohistochemistry. To identify the function of different domains within the molecule, cloned type IX and XII collagen gene constructs will be introduced into cells and tissues in culture using helper-independent retroviral vectors, followed by analysis of how the expression of such constructs affects the structure of extracellular matrices in cartilage and tendon. Finally, by studying how two, quite different forms of type IX collagen are synthesized from the same gene in two different tissues, we hope to obtain data relevant to the question of how the structure and properties of extracellular matrices may be altered by epigenetic mechanisms.